DNA sequences corresponding to influenza viral gene segments that code for the non-structural proteins (NS, gene 8), matrix protein (M, gene 7), neuraminidase (Na, gene 6) and gemagglutinin (HA, gene 4) were cloned in a plasmid in E. coli. The cloned NS DNA was employed to map mRNA coding the non-structural proteins derived from gene 8 using the S1 nuclease technique. Two separate mRNA's different in size were identified, one responsible for the NS1 and the other for the NS2 polypeptide. The NSI mRNA appeared to be a continuous transcript, while the NS2 MRNA contained an interruption produced by splicing. Cloned DNA derived from the genes for the NS proteins, NA and HA contained a complete representation of their respective genes. These cloned DNA genes are thus suitable for study of all phases of influenza gene regulation and expression. The cloned sequences also can be used to attempt to convert DNA into functional influza virion RNA. Also, heterogeneous, non-viral oligonucleotides corresponding to the 5'-terminus of viral mRNA were present in cloned DNA suggesting that a variety of cellular RNA sequences are utilized to prime influenza viral mRNA synthesis.